diff --git a/apps/api/src/ldap/ldap-sync.scheduler.ts b/apps/api/src/ldap/ldap-sync.scheduler.ts
index 6c30936..11dd8aa 100644
--- a/apps/api/src/ldap/ldap-sync.scheduler.ts
+++ b/apps/api/src/ldap/ldap-sync.scheduler.ts
@@ -64,6 +64,7 @@ export class LdapSyncScheduler {
             bindDn: config.bindDn,
             bindPassword: config.bindPassword,
             searchFilter: config.searchFilter,
+            groupFilterDns: config.groupFilterDns,
             fieldMappings: config.fieldMappings,
           },
           config.tenantId,
diff --git a/apps/api/src/ldap/ldap.controller.ts b/apps/api/src/ldap/ldap.controller.ts
index 61358d8..f61e674 100644
--- a/apps/api/src/ldap/ldap.controller.ts
+++ b/apps/api/src/ldap/ldap.controller.ts
@@ -131,6 +131,31 @@ export class LdapController {
     });
   }
 
+  /**
+   * GET /ldap/groups - Discover AD groups/OUs under the configured base DN,
+   * for building a selective import filter (groupFilterDns).
+   */
+  @Get('groups')
+  @Roles(Role.ADMIN, Role.SUPER_ADMIN)
+  async listGroups(@Req() req: any) {
+    const tenantId = req.tenantId;
+    if (!tenantId) {
+      throw new BadRequestException('No tenant context');
+    }
+
+    const config = await this.ldapConfigService.getConfig(tenantId);
+    if (!config) {
+      throw new NotFoundException('No LDAP config found for this tenant');
+    }
+
+    return this.ldapService.listGroups({
+      serverUrl: config.serverUrl,
+      baseDn: config.baseDn,
+      bindDn: config.bindDn,
+      bindPassword: config.bindPassword,
+    });
+  }
+
   /**
    * POST /ldap/sync - Trigger manual sync (D-14 "LDAP synchronisieren" button).
    * Returns sync results with created/updated/deactivated counts.
@@ -157,6 +182,7 @@ export class LdapController {
         bindDn: config.bindDn,
         bindPassword: config.bindPassword,
         searchFilter: config.searchFilter,
+        groupFilterDns: config.groupFilterDns,
         fieldMappings: config.fieldMappings,
       },
       tenantId,
diff --git a/apps/api/src/ldap/ldap.service.ts b/apps/api/src/ldap/ldap.service.ts
index 7722e32..2c09112 100644
--- a/apps/api/src/ldap/ldap.service.ts
+++ b/apps/api/src/ldap/ldap.service.ts
@@ -1,5 +1,5 @@
 import { Injectable, Logger } from '@nestjs/common';
-import { Client } from 'ldapts';
+import { Client, Entry } from 'ldapts';
 import { PrismaService } from '../prisma/prisma.service';
 import { forTenant } from '../prisma/prisma-tenant.extension';
 import { UserService } from '../user/user.service';
@@ -25,12 +25,23 @@ interface LdapConfigData {
   bindDn: string;
   bindPassword: string;
   searchFilter: string;
+  groupFilterDns: string[];
   fieldMappings: Array<{
     ldapField: string;
     tesseraField: string;
   }>;
 }
 
+/**
+ * A discovered AD group or organizational unit, returned by listGroups()
+ * for the admin to pick from when building a selective import filter.
+ */
+export interface LdapDirectoryEntry {
+  dn: string;
+  name: string;
+  type: 'group' | 'ou';
+}
+
 /**
  * LDAP Service - DIRECTORY SYNC ONLY.
  *
@@ -77,6 +88,53 @@ export class LdapService {
     }
   }
 
+  /**
+   * Discover groups and organizational units under the configured base DN.
+   * Used by the admin UI to build a selective import filter (groupFilterDns).
+   * Read-only directory query using the service-account bind.
+   */
+  async listGroups(config: {
+    serverUrl: string;
+    baseDn: string;
+    bindDn: string;
+    bindPassword: string;
+  }): Promise<LdapDirectoryEntry[]> {
+    const client = new Client({ url: config.serverUrl });
+
+    try {
+      await client.bind(config.bindDn, config.bindPassword);
+
+      const { searchEntries } = await client.search(config.baseDn, {
+        filter: '(|(objectClass=group)(objectClass=organizationalUnit))',
+        attributes: ['cn', 'ou', 'dn'],
+        scope: 'sub',
+      });
+
+      return searchEntries.map((entry) => {
+        const dn = entry.dn;
+        const isOu = /^ou=/i.test(dn);
+        const rawName = isOu ? entry['ou'] : entry['cn'];
+        const name = Array.isArray(rawName)
+          ? String(rawName[0])
+          : rawName
+            ? String(rawName)
+            : dn;
+
+        return {
+          dn,
+          name,
+          type: isOu ? ('ou' as const) : ('group' as const),
+        };
+      });
+    } finally {
+      try {
+        await client.unbind();
+      } catch {
+        // Ignore unbind errors
+      }
+    }
+  }
+
   /**
    * Sync users from LDAP directory for a specific tenant.
    *
@@ -122,12 +180,13 @@ export class LdapService {
       // Sanitize search filter (T-02-16: LDAP injection prevention)
       const sanitizedFilter = this.sanitizeSearchFilter(config.searchFilter);
 
-      // 3. Search LDAP directory
-      const { searchEntries } = await client.search(config.baseDn, {
-        filter: sanitizedFilter,
+      // 3. Search LDAP directory, applying the group/OU filter if configured
+      const searchEntries = await this.collectSearchEntries(
+        client,
+        config,
+        sanitizedFilter,
         attributes,
-        scope: 'sub',
-      });
+      );
 
       // Track all DNs found in this sync for deactivation logic
       const syncedDns: string[] = [];
@@ -252,6 +311,68 @@ export class LdapService {
     return result;
   }
 
+  /**
+   * Run the directory search for syncUsersForTenant, applying the selective
+   * group/OU import filter (groupFilterDns) when one is configured.
+   *
+   * - Empty groupFilterDns: single search of baseDn with sanitizedFilter
+   *   (identical to pre-filter behavior, backward compatible).
+   * - Non-empty groupFilterDns: split into OU DNs (used as extra search
+   *   bases) and group DNs (matched via memberOf on the base search).
+   *   Results are merged and deduped by entry dn.
+   */
+  private async collectSearchEntries(
+    client: Client,
+    config: LdapConfigData,
+    sanitizedFilter: string,
+    attributes: string[],
+  ) {
+    if (!config.groupFilterDns || config.groupFilterDns.length === 0) {
+      const { searchEntries } = await client.search(config.baseDn, {
+        filter: sanitizedFilter,
+        attributes,
+        scope: 'sub',
+      });
+      return searchEntries;
+    }
+
+    const ouBases = config.groupFilterDns.filter((dn) => /^ou=/i.test(dn));
+    const groupDns = config.groupFilterDns.filter((dn) => !/^ou=/i.test(dn));
+
+    const entriesByDn = new Map<string, Entry>();
+
+    for (const ouBase of ouBases) {
+      const { searchEntries } = await client.search(ouBase, {
+        filter: sanitizedFilter,
+        attributes,
+        scope: 'sub',
+      });
+      for (const entry of searchEntries) {
+        entriesByDn.set(entry.dn, entry);
+      }
+    }
+
+    if (groupDns.length > 0) {
+      const memberOfClauses = groupDns
+        .map(
+          (dn) => `(memberOf=${LdapService.escapeLdapFilterValue(dn)})`,
+        )
+        .join('');
+      const combinedFilter = `(&${sanitizedFilter}(|${memberOfClauses}))`;
+
+      const { searchEntries } = await client.search(config.baseDn, {
+        filter: combinedFilter,
+        attributes,
+        scope: 'sub',
+      });
+      for (const entry of searchEntries) {
+        entriesByDn.set(entry.dn, entry);
+      }
+    }
+
+    return Array.from(entriesByDn.values());
+  }
+
   /**
    * Sanitize LDAP search filter to prevent injection (T-02-16).
    * Escapes special characters per RFC 4515.